The Nuclear Regulatory Commission has launched a special inspection into how an excess amount of gas is in the residual heat removal system used to help shut down the reactors at TVA's Watts Bar Nuclear Power Plant near Spring City, Tenn.
Two weeks ago, TVA informed the NRC that revisions to its initial calculations had reduced the acceptable size of a void due to gases in the system that helps cool down the Watts Bar reactors during their shut down. On April 21, the accumulated gas in the Unit 1 system was found to have exceeded the acceptable value, and on April 22, the same observation was made on Unit 2.
The NRC inspectors will review the sequence of events, drawings, calculations and acceptance criteria, walk down portions of the plant's systems, evaluate TVA's response and assess the adequacy of actions to address the causes of the issues. NRC spokesman Roger Hannah said the issue identified by TVA does not warrant having to shut down either of the Watts Bar units and a report on the onsite visit this week is expected by June.
The residual heat removal system is used to complete the plant's cooldown process at lower pressures and also provides important functions during certain accident scenarios. Both of the reactors at Watts Bar remain operating at full power,
"Both units at Watts Bar Nuclear Plant continue to operate safely, while we monitor the performance of our multiple, redundant plant safety systems," TVA spokesman Jim Hopson said Monday.